Pressure reducing and conditioning valves are sometimes installed in a centerline horizontal position. These valves can range to in excess of 15 feet long and weigh several thousand pounds. When maintenance is performed, massive internal components are generally removed horizontally through the body/bonnet access. Removal of the components is generally not a concern because alignment is not an issue.
However, during the re-assembly process stable alignment is critical. In order to ensure proper alignment, complete assemblies of valve internals are assembled prior to installation. Creating complete assemblies of valve internals can create problems because the techniques used to join the valve components may be detrimental to the materials used in the construction of the valve, or require larger valve containments. Additionally, handling these assemblies may be limited by their size and mass.